Software Review:Micro Orbiter 3.0

By Dr. T.S. Kelso

July/August 1997

[Note: This product is no longer available. - TS]

One of the most common questions I get when talking to satellite tracking
enthusiasts—both amateur and professional—is "what's the best
satellite tracking software currently available?" Of course, there is no %best"
package, because the features that make a particular software package great for
one person won't satisfy another. That being said, some packages are better
suited for certain tasks and without a review of the contenders, it's hard to
know which ones those are.

That being said, I'd like to start of with a review of Micro Orbiter
3.0. Of all the packages I've had a chance to look at, it is one of the few
that will still run on a PC under MS-DOS and provides stunning graphics
while doing so. It will also run in full-screen mode under newer operating
systems such as Windows 95, but running in a standalone window requires
some extensive configuration (instructions for which are not included in the
documentation). Let's take a closer look at how Micro Orbiter 3.0 stacks
up.

Installation and Documentation

Micro Orbiter 3.0 Release 4.2, written by Peter D. Armstrong of
Precision Software Solutions, comes on three 3.5-inch diskettes together with an
82-page users guide, a command summary/quick start and reference summary card,
and a postage-paid registration card—it even comes with a pen to use for
filling out the registration card! Precision Software Solutions has made every
effort to make installation a snap. The installation instructions are very
simple and the process itself is very straightforward. Overall, it took me less
than five minutes to install the software and get the program up and running.
And, the entire installation (including the optional US-only airport data) takes
up just over 4 megabytes of disk space. The documentation is thorough, well
organized, and easy to read.

Features

If you are serious about your satellite tracking, your first concern when
evaluating a satellite tracking package is to determine what kind of orbital
model is used. Since most of us rely on the NORAD two-line element sets as our
data source, it is important that a satellite tracking program include the SGP4
and SDP4 orbital models. Micro Orbiter 3.0 incorporates not only SGP4 and
SDP4 but also includes the older SGP and the newer (but never implemented) SGP8
and SDP8.

Micro Orbiter 3.0 will allow for tracking of up to 20 satellites from
a database of 65,535 satellites—more than enough, since NORAD only tracks
about 7,500 today. Options for how to display these satellites abound, with no
less than ten different projection modes:

Mercator (see figure 1)

Orthographic (see figure 2)

Armadillo

Alber's Equal-Area

Littrow

Gnomonic

Aitoff

Lagrange

Oblique Aspect

Star Chart (see figure 3)

Figure 1. Mercator projection of NOAA weather satellites.

If anything, the wealth of projections is almost overwhelming. It quickly
becomes apparent that projections were added to the program incrementally, since
the hot-key combinations, mapping features, and modes of operation vary among
the many projections. But even here, Micro Orbiter 3.0 provides a
solution by providing a pull-down menu which provides a much cleaner
presentation of the options available—I only wish it had mouse support to
make this type of access easier.

Figure 2. Orthographic projection of NOAA weather satellites.

The program has a clean, professional-looking interface and the graphics are
both fast and superb, especially for MS-DOS. Most displays include: time
(elapsed or local), range, range rate, doppler, latitude and longitude, and
azimuth and elevation. These data can also be output to a text file for more
precise analysis. And, context-sensitive help is available throughout the
program—that is, when you hit F1, you get help tailored to the part of the
program you are currently working with. The only problem I had with the
interface was using the hot key combinations. Not all of the hot key sequences
make sense (most likely the result of features being added over time) and the
command summary card has the hot keys listed in alphabetical order rather than
functionally grouped. The context-sensitive help is a great aid here and the
pull-down menus do group things functionally.

Almost everything in Micro Orbiter 3.0 is configurable to accommodate
varied user tastes. Don't like the map colors? Change them. Want to show
constellation names on your star chart? Go right ahead. The options for displays
are well thought out, right down to allowing night-vision colors for the star
chart (see figure 3).

Figure 3. Sky projection of NOAA 14 satellite.

Micro Orbiter 3.0 is best suited to real-time tracking. While, it does
have features to do some rudimentary time control, such as advancing manually or
automatically (in most modes) or jumping to a particular time, this control
lacks flexibility. For example, there is no way to look at a satellite's
position prior to the epoch of the element set being used—the program
assumes such a projection would be invalid and provides no option to override
it. These limitations can make analysis difficult.

In real-time tracking mode, however, Micro Orbiter 3.0 excels. There
are features to calculate upcoming passes—visible or otherwise—and
event timers which count down to inform you of when an upcoming event (rise,
set, peak elevation) will occur. In fact, the user can set hundreds of
event timers. The user can even generate pass schedules for large numbers of
satellites at once, although this output goes to a text file. Displays show the
position of the sun and moon and will indicate when a satellite is illuminated,
above the observer's horizon, and visible. For star backgrounds, Micro
Orbiter 3.0 uses the Yale Bright Star Catalog of over 9,000 stars
(down to magnitude 8.2).

Last, but not least, is the ability to input orbital data. The layout here is
not as clear as other parts of the program, but the context-sensitive help will
guide you through. It is quite easy to update, append, merge, or replace
elements in the master database using text files containing NORAD two-line
element sets found on the Celestial WWW site and many other sources. The only
apparent limitations are in the delete function which will only work with a
single satellite at a time—making it difficult to clear out the file and
start over, and the search function—which requires a case-sensitive exact
match.

Selecting 20 satellites out of 65,535 to begin tracking might seem like a
daunting task, but Micro Orbiter 3.0 does provide a mechanism to track
groups of satellites with a little pre-configuration. By defining a list of
satellites in a text file and then creating an MS-DOS batch file to make
this file the default tracking file, it is easy to start up tracking your
favorite weather, amateur radio, or visible satellites.

Benchmarking

The bread and butter of any satellite tracking program lies in the accuracy
of its predictions. All the fancy graphics in the world won't amount to much if
the results can't be relied upon. In an earlier column on benchmarking ("Real-World Benchmarking,"Satellite Times,
Volume 3, Number 2), we demonstrated that the basic routines used in my TrakStar program were able
to predict satellite positions within about one-tenth of a
degree—TrakStar has also been validated against test cases for SGP4
and SDP4 provided by US Space Command.

As such, we can use the output from TrakStar and compare it to that of
Micro Orbiter 3.0 to give us an idea of how well the latter performs. I
used NORAD Element Set 201 for Mir and generated ephemerides (tables of
predictions) of ECI position and velocity and latitude, longitude, and altitude
for the period 1200-1230 UTC on 1997 April 17; and azimuth, elevation, and range
for the period 0157-0207 UTC on 1997 April 18 for a limited test case. The
results are shown in table 1.

Table 1. Maximum differences between TrakStar and
Micro Orbiter 3.0.

X positionm

Y positionm

Z positionm

X velocitym/s

Y velocitym/s

Z velocitym/s

0.000

0.000

0.000

0.000

0.000

0.000

Latitudedeg

Longitudedeg

Altitudekm

0.1810

0.0001

3.299

Azimuthdeg

Elevationdeg

Rangekm

0.0000

0.3481(at ~1.5° elevation)

0.000

There was no difference at all in the SGP4 position and velocity predicted by
Micro Orbiter 3.0, indicating a good implementation of the NORAD model.
There was some small difference in the latitude and altitude (but not the
longitude) of Mir, most likely due to a difference in the model of the
earth's shape used by the two programs—TrakStar uses WGS 72;
Micro Orbiter 3.0 uses WGS 84. Finally, there was no difference in
azimuth or range between the two programs, but there was a difference in
elevation, which was inversely proportional to the elevation. This result is
probably due to the fact that TrakStar models atmospheric refraction at
standard temperature and pressure and Micro Orbiter 3.0 does not.
Overall, a very good performance by Micro Orbiter 3.0.

It should be noted that by differences, I do not mean to imply that Micro
Orbiter 3.0 is in error—only that it uses different modeling
assumptions than TrakStar. These differences are well within the error
tolerance of the SGP4 orbital model (5 kilometers with 90 percent confidence)
and should not be treated as significant.

Summary

Micro Orbiter 3.0 is a superb choice for real-time satellite
tracking—especially if you are still using MS-DOS. Installation is
a snap, taking less than five minutes to get it up and running. Orbital
predictions are quick and accurate, based upon the NORAD orbital models, and an
easy mechanism for importing two-line element sets is provided. The interface is
professional and graphics are excellent, rivaling even some Windows-based
packages. It features a wealth of map projections and options for configuring
them which, although cumbersome to access via hot keys, are easy to access via
pull-down menus. And, at a price of $49.95 (plus $4 shipping and handling), it
is a hard deal to beat.

If you have any questions or comments regarding this column, please feel free
to contact me at
TS.Kelso@celestrak.com. Until next
time, keep looking up!